Reflecting electric lamp



' Patented Oct. 29 1940 Q UNITED sTATas PATENT OFFICE.

REFLECTING ELEc'rmo'LAMP Clarence Birdseye, Gloucester, Mass., assignor, by mesne assignments, to Birdseye Electric Corporation, Gloucester, Mass, a. corporation of 4 Massachusetts =i)riginal application December 28, 1935, Serial No. 56,502. Divided and this application November 26, 1938, Serial No. 242,615

2 Claims. (Cl. 176-34) This invention relates to devices for directing other way is different in chemical composition or radiant energy in the form of light rays or nonin light transmitting properties from the reluminous rays into definite working areas. An fleet n po t on of t e bulb. important field of use of the invention is in con- Thus the transmitting portion of the bulb be- 5 nection with incandescent lamps having some comes in effect a window with certain char- 5 part of the bulb arranged to act as an eflicient acteristics that are different from the rest of reflector for the purpose of directing and conthe bulb, and may be of any other glass or maserving the light for useful work in selected terial having specific optical properties different areas, from those of the rest of the bulb, and which More particularly the invention is concerned will in P determine the Wave length di 10 with lamps designed for special purposes, and tribution of the transmitted light, and through with respect to which not only is the direction. which it is desired to transmit the light from of the rays of importance, but also the quality of e l mp. A adva e of t s co t uctionis light. For exam le, in stage lighting where 001- tha h refl n p t of t bulb may be ored efiects are desired, this is often accomcompleted independently of the rest of the bulb l5 plished by placing standard lamp bulbs behind and a reflecting co i pp t i s n erior suitable color screens, usually made of gelatine, surface while the latter is fully accessible and The color of the light shining on the stage may before the window portion is sealed thereto. The

be, changed by the operator of a key-board, each end Portion cover gleSS y be also s paratekey controlling a single lamp or a series of given 1y prepared with due consideration to its coefv color. In large installations many lamps, each ficient of expa and en herm tically with its screen and external reflector, are emsealed by fusion to the rim of the reflecting ployed. Gelatine screens are relatively cheap, portion.

but their life is short and the labor cost of re- Th wind w of di imi r class m y b s aled placing them perhaps once a week is high. Per-, 0r fused about i s margin to the reflecting p manent color screens of glass are heavy and ex-' tion of a bulb in a symmetrical position on a pensive, and must be replaced frequently because line with the main axis or with the axis of the of breakage. Color screens produced by coating fl c g portion of the bulb- Its Size, in this the bulb surface are often inefficient transmitters P t o y approximate t e m x mum diamof light, and the temperature of such coatings eter of the bulb, although itneed not necessarily during the periods of use is high enough to cause be hemispherical in shape, since a flatter curve rapid destruction of most colors and binders.' would be equally satisfactory and would q e Bulbs made entirely of colored glass are satisless of the dissimilar glass. The rest Of the bulb factory within limits for the purpose, except for m y preferably be silvered over i inside r uttheir first cost, which is generally very high, side surface of plain glass, so that all of the light 35 since the colored glass is a'relatively expensive from the source would either be transmitted material. through the window directly as direct light, or

I have found that I can reduce the cost and after-a single reflection from the silvered surface. upkeep of such an installation for producing If the transmitting window in a bulb of this '40 colored light effects, or any installation where shape were o smaller size than the um 40 reflecting lamps may be usefully employed and diameter of the bulb, and if the rest of the bulb at the same time eliminate the need of external were silvered, or otherwise made into a highly reflectors, thus further reducing cost and the efficient reflecting surface, it is obvious that some space required for the installation, and secure of the reflected lig would be pp d th n these desirable results with an appreciable inthe silvered surface, and would be reflected sev- 45 crease in lighting efliciency. This I achieve by oral times before leaving the bulb. This would employing a composite bulb having one part result in a measurable decrease in lighting efmade into a highly efiicient reflector, and prefficiency, and transmitting windows smaller than F erably of such shape and disposition relative to the maximum diameter of the bulb would .be

" the light source within the bulb that all reflected employed only when the efficiency was of secrays pass directly out of the lamp through the ondary importance and when the cut-off angle transmitting area of the bulb, after not more was the determining consideration. than a single reflection, and by fusing to such a Symmetrical lamps of other shapes than the reflecting portion of the bulb a transmitting porstandard shape may be readily constructed in tion which is made of colored glass,'or in some this way, but in all such cases the diameter of 55 the window is preferably that of the maximum bulb diameter in order to obtain highest efficiency; and in general, substantially all the rest of the bulb may be utilized as an efilcient refiector. The reflector, besides directing most of the light from the source through the window, also serves to hood the light source and thereby mask all parts of the bulb except the transmitting window.

ID A window of dissimilar material may alternatively be located in the side walls of a bulb, although a less efiicient result will be secured because of trapped rays and multiple reflection, unless either the window covers approximately half the area of a bulb symmetrical about its main axis, or unless an asymmetrical bulb is used which has been designed to have such shape and provided with a reflecting surface such that all of the light leaves the bulb through the window either as direct light or after a single reflection. Such a bulb with a colored window occupying a part of the side wall, and with a sloping neck reflector, and with the rest ofthe bulb surface serving as a reflector to reflect light directly out through the colored window is an eflicient lamp for stage lighting effects. I

In this same manner a quartz window may be sealed into a glass bulb for transmitting ultraviolet light rays, for example. In general I wish to include within the scope of this invention all composite lamp bulbs 01 the type hereinafter claimed which have windows of different transmitting properties than the rest of the bulb and used with reflecting surfaces integral with the bulb to reflect light out through the window. It may be desired in some cases to produce a diffused light from such window-bulbs andthis may be obtained by frosting the transmitting portion of the bulb, or by frosting the glass under the reflecting deposit, or in some other way producing a diffusing reflecting surface, as explained in Patent No. 2,144,673, issued Jan. 17, 1939, to myself and Pincus Deren.

These and other features of the invention will be best understood and appreciated from the following description of two preferred embodiments thereof selected for purposes of illustration and shown in the accompanying drawing, in which,

Fig. 1 is a viewin elevation, partly in section, of a lamp of symmetrical shape, and

Fig. 2 is a similar view of a lamp shaped to direct a beam at right angles to its major axis.

The lamp shown in Fig. 1 has a composite bulb in which is included a cylindrical neck portion III, a flaring or conical portion II and a curved or rounded end portion l2. The portions l0 and II may comprise any glass commonly used in commercial bulbs while the end portion I2 is herein shown as being red glass fused into the body of the bulb. The end or window portion I2 is of the full diameter of the bulb and of slightly flattened convexity in contour.

The lamp includes the usual metallic base It and mount l4 through which project lead-in wires l5 for a coiled filament IS. A desirable type of filament is that disclosed in the pending application of Charles Spaeth, Ser. No. 15,605,

consisting in a wire helix having a core of tungsten or the like therein and being wound with its core in a secondary helix. As herein shown the filament serves as a concentrated light source and is supported substantially within the plane of maximum bulb diameter so that it is hooded by the coated portion of the bulb.

The bulb is provided upon a predetermined portion of its surface with an interior reflecting coating l1 and for this purpose'metallic silver may be satisfactorily employed. In the illustrated lamp the reflecting coating extends 5 from the line of maximum bulb diameter to a line in the neck of the bulb, and it is supplemented by a reflecting disk I 8 surrounding and insulated from the lead-in wires just beyond the inner end of the mount I4. 10

In the lamp of Fig. 1 the light rays emanating fromthe filament l6 pass either directly'out through the red cover glass portion |2 or they are reflected by the coating 'I'I or the disk It! and pass out as reflected light through the por- 15 tion |2. The coating further, acts to hood the light of the lamp in all directions except where it is wanted, with the result that substantially all the light energy ofthe lamp is conserved and directed into a single restricted beam 20 of red light.

The lamp of Fig. 2 is similar in construction to that already described but of somewhat diflervent shape. Its composite bulb has a cylindrical neck 20 and a bowl portion 2| disposed with its 25 axis at right angles to the axis of the neck, and both made of clear glass of any commercial type. The bowl portion 2| may be circular or oval in cross section (in a plane perpendicular to the plane of the paper) and has a curved or rounded 30 .face 22 of red glass fused, as before, into the body of the bulb.

The lamp is provided with the usual base 23, and sealed-in mount 24 from which project lead-in' and supporting wires 25. In this case the coiled filament 26 is supported in a plane substantially perpendicular to the axis of the portion 2| instead of perpendicular to the principal 'axis of the lamp.

The inner end of the'neck 20 and the entire 40 inner surface of the bowl portion 2| are provided with a coating of metallic silver 21 or other eflicient reflecting material and this is supplemented by a reflecting disk 28 surrounding the lead-in wires and supporting wires 25 and so disposed as to constitute in effect a continuation of the surface of the bowl portion 2|. On account of the particular shape of the reflecting surface, which as shown may be substantially parabolic all rays emanating from the filament arecollected into a single concentrated beam and directed outwardly through the red glass portion 22 of the bulb.

While I have illustrated only lamps having red glass window portions it will be understood 5 that I contemplate the employment of any desired material in this portion of the lamp. For example, different colors may be secured by introducing metallic or metalloid ingredients into the glass composition, or quartz or other light 60 alloy may be substituted if desired; also that my invention is in no sense limited to any specific 70 type of filament. I

It will be seen that by the present invention 1 provide a compact and eflicient unit which may be installed in small space or manipulated conveniently by the user and which is useful in 76 a broad field of lighting, therapeutic treatment and radiant energy application of all sorts.

The present application is a division of my prior application Serial No. 56,502, filed December 28, 1935 now Patent No. 2,144,400, which I have restricted to the invention as embodied specifically 'in the lamp of Fig. 2.

Having thus described my invention, what I and the bulb having a convex flattened transmitting window of the full diameter of the bulb, fused into the bulb and having difierent optical characteristics from the glass of the body portion of the bulb.

2. A reflecting electric lamp comprising a com- I posite glass bulb having a neck merging into an outwardly flaring substantially conical portion which is provided with an internal metallic coating, a coiled coil filament located substantially symmetrically in the axis of the bulb, a convex cover portion fused to the outer edge of said conical portion about its line of maximum diameter, having diflerent optical characteristics than said conical portion,.and providing a window'ior the concentrated beam defined by the reflecting coating of the bulb.

. CLARENCE BIRDSEYE. 

